Front Axle Disconnect and Ring Gear Rotation

CarbonSteel

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Can anyone definitely confirm whether or not the ring/pinion gear and front driveshaft turn when NOT in 4x4 mode? I see a few posts where different folks think it does not and I was wondering if anyone knows for sure.

Thanks in advance and apologies if this has been asked before.





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Gorilla57

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The R&P/front driveshaft DO NOT rotate unless you are in 4WD. The driver's front axle does spin the spider gears inside the diff, but the R&P will sit still. The passenger side outer axle also spins, but at the FAD, the disconnect won't allow the inner axle to rotate.
 
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CarbonSteel

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The R&P/front driveshaft DO NOT rotate unless you are in 4WD. The driver's front axle does spin the spider gears inside the diff, but the R&P will sit still. The passenger side outer axle also spins, but at the FAD, the disconnect won't allow the inner axle to rotate.
Many thanks for the confirmation--I suspected as much after recently installing front and rear axle temperature gauges. Without the ring gear spinning the oil will not touch the sensor (which is ok).

Before I drill and tap the permanent front cover (Metal Cloak) I want to be sure that with the ring gear spinning the oil will hit the sensor. Since the oil flow is opposite on the front axle (versus the rear), I may have to reposition the sensor. I have a 4x4 excursion planned soon, so I will know during that.

Thanks again!
 

oceanblue2019

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The R&P/front driveshaft DO NOT rotate unless you are in 4WD. The driver's front axle does spin the spider gears inside the diff, but the R&P will sit still. The passenger side outer axle also spins, but at the FAD, the disconnect won't allow the inner axle to rotate.
Actually I think one missed point:

All the above happens, but the passenger inner axle also spins, but opposite direction, due to being driven by the drivers side axle driving the differential spider gears. The outer side passenger is as per above.

The FAD is the clever trick that allows front axle to free-wheel with less friction losses versus spinning ring, pinion, and front drive shaft and the disconnect occuring at the transfer case.
 

MarkY3130

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Actually I think one missed point:

All the above happens, but the passenger inner axle also spins, but opposite direction, due to being driven by the drivers side axle driving the differential spider gears. The outer side passenger is as per above.

The FAD is the clever trick that allows front axle to free-wheel with less friction losses versus spinning ring, pinion, and front drive shaft and the disconnect occuring at the transfer case.
This is the correct answer.

Also note that the ring gear and driveshaft will move a little while you are driving. I noticed this once I went to an aftermarket driveshaft with a grease nipple. I checked the location of the nipple after driving and it would be in a different location. Got me somewhat concerned that I screwed something up when installing axle shafts so I put it up on jack stands and could not get the drive shaft to spin. So I put a camera down there and drove a bit and the driveshaft was not spinning, but every once in a while it would turn just a little bit. The ring gear must move a little bit under some driving conditions.
 

oceanblue2019

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This is the correct answer.

Also note that the ring gear and driveshaft will move a little while you are driving. I noticed this once I went to an aftermarket driveshaft with a grease nipple. I checked the location of the nipple after driving and it would be in a different location. Got me somewhat concerned that I screwed something up when installing axle shafts so I put it up on jack stands and could not get the drive shaft to spin. So I put a camera down there and drove a bit and the driveshaft was not spinning, but every once in a while it would turn just a little bit. The ring gear must move a little bit under some driving conditions.
Yup, nothing is physically stopping the ring/pinion/front drive shaft from spinning except it's typically more resistance to turn versus the front diff spiders spinning. I'm sure in some cases that resistance changes - perhaps in tight turns or certain suspension angles.
 
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CarbonSteel

CarbonSteel

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This is the correct answer.

Also note that the ring gear and driveshaft will move a little while you are driving. I noticed this once I went to an aftermarket driveshaft with a grease nipple. I checked the location of the nipple after driving and it would be in a different location. Got me somewhat concerned that I screwed something up when installing axle shafts so I put it up on jack stands and could not get the drive shaft to spin. So I put a camera down there and drove a bit and the driveshaft was not spinning, but every once in a while it would turn just a little bit. The ring gear must move a little bit under some driving conditions.
I agree with your observations. There have been a couple of times the front gauge gives a reading and it is typically after a highway drive or after backing up.
 

Gorilla57

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Good point about the inner passenger front axle spinning the other direction. Didn’t even think about that, an open diff “requires” it to spin the other way since the R&P aren’t moving. I’ve noticed my front driveshaft does not spin when driving. It’s a heavy Adams 1350 setup and the grease zerk has been pointing the same way for a couple hundred miles. This heavy shaft combined with a new gear set probably has enough friction that it hasn’t moved.
 

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